This invention relates to bag houses having tubular filter bags vertically suspended in the house and more particularly to the construction of the cell plate to which the open ends of the bags are attached.
FIG. 1 of the drawings illustrates a typical bag house to which the present invention relates, the bag house having a ceiling 11, hopper floor 12 and side walls 13 forming a completely enclosed structure and a horizontal cell plate 14 dividing the interior of the house into upper and lower compartments. The cell plate has a plurality of openings therethrough. A plurality of tubular cloth filter bags 15, each having a closed upper end and an open lower end, are suspended in the bag house, the open ends of the bags being connected to the cell plate so that the open end of each bag is in communication with one of the cell plate openings. Dirty air enters through inlet 16 into the lower compartment of the house and flows up into the bags through openings in the cell plate. As the air passes through the bag walls the entrained dirt particles are caught on the inside of the tubes and the clean air exits through outlet 17 from the upper compartment of the house.
There are several ways in which filter bags have been attached to the cell plate. One commonly used method is to punch holes through the flat cell plate, one for each bag to be used. A cylindrical thimble of relatively thin-gauge material is secured in each hole with one end of the thimble being rolled onto the lip of the cell plate opening and with the body of the thimble projecting upwardly from the cell plate. The open end of the bag fits down onto the outer surface of the thimble body and is clamped thereto by a band passing around the outside of the bag.
This manner of attachment has advantages in that the interior of the bag adjacent the cell plate is protected, by the height of the thimble inside the bag, against abrasion by the entrained dirt particles as they flow across the lower chamber and then up into the bag. Also, during the times when a workman enters the bag house for inspection or maintenance of the filter bags and moves about on the upper surface of the cell plate, the thimble will protect the bag against being kicked accidentally by the foot of the workman. Similarly, if a ladder is used inside the upper compartment with its legs resting on the cell plate, the thimble will prevent the ladder legs from slipping and falling through a cell plate opening.
On the other hand, forming the thimble and fastening them to the cell plate openings is a relatively expensive procedure. Similarly, the attachment of the bags to the thimbles by the use of band clamps is a tedious and time-consuming process which increases the cost of initial installation and subsequent maintenance.
In addition, since the thimbles are made of relatively thin-gauge material, they add no significant strength to the floor. Since the many closely spaced openings through the cell plate weaken the plate, stiffening members must be secured to the cell plate to provide the necessary rigidity thereto and to prevent warpage of the plate as it is welded to the bag house walls or is subjected to hot gases.
Another form of bag attachment involves the use of bags having a flexible spring rim at the lower end thereof, the rim having a groove extending around the outer periphery of the bags. In such case the spring is deformed to allow the lower end of the bag to be fitted into a punched hole of the cell plate. The spring is released so that it resumes its original circular shape with the lip of the cell plate hole received within the groove.
This form of attachment is somewhat less expensive since no thimble is needed and the bag may be connected to the cell plate more rapidly and without the use of tools. However, the interior of the bag is now immediately adjacent the cell plate and the lower end of the bag is thus subject to abrasion by dirt particles as they change from a generally horizontal flow and move vertically up into the bag. Abrasion is a considerable factor in maintenance since a bag must be changed before a hole is abraded therethrough. Likewise, the bag is unprotected immediately above cell plate level and may be easily damaged by a workman's foot. Additionally, relatively costly stiffening members are required to strengthen the cell plate against warpage from heat or the weight of a workman thereon.
It is the object of the present invention to provide a manner of securing filter bags to cell plates which obtains the advantages of both of the forms mentioned above but without the disadvantages thereof and which also provides an increase in efficiency of the apparatus.